The present invention is directed to a revolutions per minute (RPM) regulation device for a hand-held electric tool with the device insertable as a separate block-like unit or module into a space between the tool handle and drive motor housing of the tool. The control device includes an RPM sensor for registering the RPM of an electric motor located in the drive motor housing. Further, the invention is directed to a method of manufacturing the encapsulated electronic components of the control device for hand-held electric tools of different types.
It is advantageous and known in electric tools of the above type, for instance, hammer drills and drilling tools, as well as hand-held grinding and cutting tools, to provide an electronic RPM control device for the drive motor inserted as a unit into a space between the handle and the drive motor housing. This space located in the region between the handle and the drive package is advantageous, because with regard to the required connections, it is located on the shortest path between the handle, where the electric energy is usually supplied by a cable and controlled by a switch, and the drive motor where the electric energy is used. Moreover, in the region adjacent the motor it is possible to install the RPM sensor required for RPM control (tachogenerator) directly at the RPM control circuit usually provided as a separate block-like encapsulated electronic component with the advantage of short and less malfunction-prone connections. In addition, in this arrangement, the RPM sensor can extend through a housing opening into the region of the drive motor for approaching, as closely as possible, to a rotating part whose RPM is to be registered. Accordingly, nearly all possible tachometer principles can be utilized, possibly the combination of a rotating magnetic ring, whose magnetic field flux changes are acquired or registered by induction coils along with a Hall sensor. It is also possible to use light barrier systems, for instance, known as a so-called fork-like barrier with a perforated disc.
Problems with the known RPM control device of the mentioned type result, however, that for different hand-held electric tools and for different sizes of identical electric tools, an individually adapted and manufactured RPM control device must be formed as a block-like unit or module and must always be available from storage.